Voltage disturbances and harmonics cause premature equipment failures, automation failures, erratic computer operation, lost data and data errors, burned out motors, electronic module failure, premature lighting failure and the like. There is more equipment in homes, offices and industrial facilities that is sensitive to voltage disturbances and harmonics. For example, some types of equipment that are affected by poor power quality include electronic lighting ballasts, computers, copiers, laser printers, adjustable speed drives, industrial programmable logic controllers (PLCs), medical equipment and many microprocessor-controlled devices. Some equipment also contributes to poor power quality. Poor power quality may also reduce the useful life of many types of equipment.
Thus, stable power is needed for the complex electrical installations typically encountered in today's buildings. Of course, voltage surges can be caused by lightning. However, the cause of poor power quality frequently resides in the building rather than in the electrical power distribution system outside of the building. Thus, monitoring of the power quality inside of the building, such as on selected electrical circuits, may assist in diagnosing where any problems occur. Insurance studies indicate that about one-half of the cost associated with electrical failures could be prevented by regular maintenance.
A voltage disturbance and harmonics monitor can verify and diagnose voltage sags, swells, impulses and total harmonic distortion (THD) to assist in the monitoring of power quality. Sags and swells are temporary increases or decreases in voltage that can affect the performance of equipment. Sources of such voltage events include motors, photocopiers, arcing switches, water coolers, air conditioners and some routine utility operations.
Harmonic distortion is an increasing problem due to the increase of electronic loads. A harmonic is an integer multiple of the fundamental 60 Hz waveform. Electronic loads typically convert AC voltage to DC voltage for supplying power to lower voltage electronic circuitry. This process distorts the AC voltage waveform and contributes to the “flat-topping” of the AC supply voltage, which starves other power supplies of the optimal peak voltage needed to power their loads. The more devices that are present, the greater the likelihood of this type of voltage distortion and the greater the likelihood of adverse effects on other equipment. Harmonics can also be caused by loads switching on and off, electronic ballasts in fluorescent lighting, variable speed motor drives, soft start motors, welding equipment and the like. Harmonics also affect traditional loads and wiring as well, in the form of added heat, nuisance tripping of peak detecting circuit breakers and noise on communication equipment. In general, a THD above about five percent should be investigated and mitigated where feasible.
There has therefore a need for an improved voltage disturbance and harmonic monitor for monitoring the quality of the electrical power.
A general object of the present invention is to therefore provide an improved voltage disturbance and harmonic monitor for monitoring the quality of the electrical power.
Another object of the present invention is to provide an improved voltage disturbance and harmonic monitor which is capable of monitoring power quality for all power systems throughout the world.
A further object of the present invention is to provide a voltage disturbance and harmonic monitor which includes improved surge protection for high voltage surges in the power system.
Yet another object of the present invention is to provide a voltage disturbance and harmonic monitor with low-distortion signal conditioning.
A still further object of the present invention is to provide a voltage disturbance and harmonic monitor with improved storage of sample data collected during the monitoring of power quality.
Another object of the present invention is to provide a voltage disturbance and harmonic monitor with double buffering of sample data acquired during the monitoring of power quality.
Yet another object of the present invention is to provide a voltage disturbance and harmonic monitor which utilizes direct memory access (DMA) techniques to alternately store sample data acquired during the monitoring of power quality in dual buffers.